Electrical switch with contact wiping

ABSTRACT

An electrical switch having two fixed electrical contacts which are mounted within a housing in spaced-apart, face-to-face relationship. Two movable electrical contacts are mounted in back-to-back relationship on the end of a resilient arm between the two fixed contacts. The resilient arm is engaged in its central portion by an actuating plunger which is spring-loaded to hold one pair of contacts in a normally closed position and the other pair of contacts in a normally open position. Manual movement of the plunger closes the normally open contacts and opens the normally closed contacts. Release of the plunger reverses the action. The resilient arm is bowed in its central portion where it engages the actuating plunger to produce a transverse contact wiping movement of the movable contacts whenever the contacts are opened or closed to automatically clean the contacts every time the switch is used. The fixed contacts are canted to increase contact pressure and to lengthen the contact wiping movement. The housing contains a projecting socket to provide a guide of increased bearing length for the plunger and its spring.

United States Patent 1191 Schantz [4 1 May 1, 1973 [54] ELECTRICALSWITCH WITH CONTACT WIPING Primary Examiner-J. R. Scott [75] Inventor:Spencer C. Schantz, Oconomowoc, Attorney rthur Morsen et W' 1 57ABSTRACT [73] Assignee: U.S. Controls Corp., New Berlin,

An electrlcal sw1tch having two fixed electrical contacts which aremounted within a housing in spaced- Filed; 1971 apart, face-to-facerelationship. Two movable electri- [21] Apph No; 193,294 cal contactsare mounted in back-to-back relationship on the end of a resilient armbetween the two fixed contacts. The resilient arm is engaged in itscentral 52 us. c1. ..200/164 R, 200/6 BB, 200/6 c, portion by anactuating plunger which is springloaded 200/159 A1 200/166 J to hold onepair of contacts in a normally closed posi- [51] Int. Cl. ..H0lh 1/36,HOlh 13/52 I tion and the 0ther pair of Contacts in a normally open [58Field of Search ..200/6 BB, 6 C, 16 A, position Manual movement of theplunger closes the 200/159 159 164 166 170 R normally open contacts andopens the normally closed contacts. Release of the plunger reverses theaction. [56] References cued The resilient arm is bowed in its centralportion where UNITED STATES PATENTS it engages the actuating plunger toproduce a transverse contact wiping movement of the movable coni tactswhenever the contacts are opened or closed to orse 1 3,250,882 5/1966Campbell et al... ....200/159 A x i ctomacts g l thfi swtch 3,175,0663/1965 Fiddler 200/159A use e ac S are can 6 3,261,955 7/1966 Martin.....,...200/159 A tact Pressure and 9 the Q F WlPmg 3,243,548 3/1966Kjellman 6t 61.... ....200/164 RX movement The 1101181112 Contams aPIOJeCKmg Socket 2,524,410 10/1950 Trainor ..200/ 159 A X to provide aguide of increased bearing length for the 2,951,916 9/1960 Scheffer","200/164 R X plunger and its spring, 3,185,803 5/1965 Driscoll.....200/l59 A 3,114,805 12/1963 Baomer ..200/164 R X 6 Claims, 6 DrawingFigures '1 11 1-1 ll II I "-4 1111., 1- 1. 1, HINT] IIIHHHW lll I AZPatented May 1 1973' wil ll l Z5 INVENTOR. W. C

ELECTRICAL SWITCH WITH CONTACT WIPING BACKGROUND OF THE INVENTION Thisinvention relates in general to electrical switches. In the past,difficulty due to corrosion of the contact surfaces has arisen inconnection with electrical switches which are used in a moistenvironment such as encountered in washing machines and clothes dryers.

Accordingly, the principal object of this invention is to provide anelectrical switch which contains means for automatically cleaning thecontact surfaces to prevent corrosion thereof.

Another object of this invention is to provide an electrical switch ofthe above-noted character in which the automatic cleaning of the contactsurfaces is performed in a simple and reliable manner which does notrequire the use of added parts to the switch.

A further object of the invention is to provide an electric switchhaving a novel housing assembly providing a compact arrangement while atthe same time providing a guide of increased bearing length for theplunger and its spring.

A further specific object is to provide a switch as above described inwhich the base of the housing has a projecting socket portion positionedbetween terminals and forming a guide for the lower end of the plungerand a guide for the lower portion of the plunger spring, the arrangementbeing such as to eliminate friction between the spring and the housingand between the spring and the plunger and provide maximum distancebetween bearing points for improved "quality feel."

An additional object of the invention is to provide a switch having thefixed. contacts thereof canted to increase contact pressure and tolengthen the contact wiping movement.

A further object of this invention is to provide a switch of theabove-noted character which is simpler in structure and less expensiveincost than those heretofore known in the art.

SUMMARY OF THE INVENTION In accordance with this invention, theabove-noted objects are attained by providing an electrical switchhaving at least one fixed contact and at least one movable contact whichis mounted on the end of a resilient arm facing the fixed contact. Theresilient arm is engaged in its central portion by an actuating plungerto move the movable contact into and out of contact with the fixedcontact. The resilient arm is bowed in the portion thereof which isengaged by the actuating plunger to produce a transverse contact wipingmovement of the movable contact whenever the contacts are opened orclosed to automatically clean the contacts every time the switch isused. The fixed contact is preferably canted to increase contactpressure and to lengthen the contact wiping movement. The invention alsoincludes a novel housing assembly together with novel means forsupporting and guiding the plunger in operating movement and for guidingthe plunger spring.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view ofone illustrative embodiment of the invention partially in verticalsection;

FIG. 2 is a cross-sectional view taken on the line 2- 2 ofFIG. I;

FIG. 3 is a detail front view of the actuating plunger of the embodimentillustrated in FIGS. 1 and 2;

FIG. 4 is a detail side view of the resilient arm and movable contactsutilized in the embodiment illustrated in FIGS. 1 and 2;

FIG. 5 is a detail top view of the resilient arm and contact structureshown-in FIG. 4; and

FIG. 6 is an enlargedside elevational view of the contacts showing howthe transverse contact cleaning movement is produced.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIGS. 1 and 2, oneillustrative embodiment'of this invention is contained within a housingmember 10 which is preferably made of a transparent plastic such aspolycarbonate material. The housing member 10 acts as a support for theswitch and is closed on its bottom side'and open on its top side, whichis covered by a metallic cover plate 12. The metallic cover plate 12 isattached over the top of housing member 10 by being crimped over flangedupper edges 14 and l6.-The metallic cover plate 12 extends from one sideof the housing 10 as indicated in FIG. 2 at the numeral 18 and hasopenings formed therein for receiving screws to mount the switch on aclothes dryer or other device.

Two fixed electrical contacts 22 and 24 are mounted within the housing10 in spaced-apart, face-to-face relationship on corresponding mountingelements 26 and 28. Mounting elements 26 and 28 are made out of anelectrically-conductive material such as brass and are adapted at theirlower end portions 27 and 23 to serve as electrical terminals. Twomovable electrical contacts 30 and 32 are mounted between the two fixedcontacts 22 and 24 on the end of a resilient arm 34 which is attached atone end to a brass mounting element 35 by means of a rivet 38. Theresilient arm 34 is made of an electrically-conductive spring materialsuch as phosphor bronze, and the brass mounting element 35 is adapted atits lower portion 36 to act as an electrical terminal. The fixedcontacts 22 and 24 are preferably canted at a slight angle with respectto the horizontal (referring to the drawings) to increase the contactpressure and increase the wiping movement of the contacts.

The resilient arm 34 is bowed in its central portion as shown in FIG. 4and the central portion is engaged by an actuating plunger 40 (seeFIG. 1) which is normally spring-loaded in the upward direction by meansof a compression spring 42. Actuating plunger 40 is made of aninsulating material. The upward movement of the plunger 40 is limited byan abutment 44 which bears against the cover plate 12 and limits theupward movement thereof. The upper end of actuating plunger 40 extendsthrough an opening in the top of cover plate 12 and is attached to abutton member 46 which is pushed to operate the actuating plunger 40.The compression spring 42 fits into a tubular projecting socket 48 inthe bottom of the housing 10 and abuts against an annular shoulder 50 inthe tubular socket 48. The lower portion of the plunger 40 is tapered asshown in FIG. 3 at 52 so as'to prevent friction between the actuatingplunger and the compression spring 42 when the plunger is pushed down.There is a short cylindrical end 51 which is guided in a cylindricalprojection 53 of the tubular socket. The compression spring 42 makescontact at its upper end with the outside diameter of the taperedportion 52 of plunger 40 and makes contact at its lower end with theinside diameter of tubular socket 48 above the shoulder 50. The tubularprojecting socket 48 serves the purpose of permitting a relatively longcompression spring 42 to be used and also provides a guide of increasedbearing length for the plunger. It should be noted that the projectingsocket 48 is positioned in the space between the electrical terminals27, 23, and 36.

'This positioning provides the advantages noted above without increasingthe size of the housing or interfering with the electrical connectionsin any way.

The resilient arm 34 passes through an opening 54 in actuating plunger40 (see FIG. 3). When the plunger 40 is pushed downwardly, the resilientarm 34 is pushed downwardly along with it, carrying the two movablecontacts 30 and 32 downwardly and making contact between the twocontacts 22 and 32 (see FIG. 6). After contact has been initially madebetween the two contacts 22 and 32, as shown by broken lines in FIG. 6,the continued downward I movement of plunger 40 straightens out the bendin the central portion of the resilient arm 34 and causes the movablecontact 32 to move transversely and make a wiping movement over thesurface of the stationary contact 22 to the full line position of FIG.6. When the plunger 40 is released, the movable contact 32 makes anotherwiping movement over contact 22 before it breaks contact and then, asthe contact 30 moves upwardly and initially touches the contact 24, asshown by broken lines in FIG; 6, a similar transverse wiping movement isproduced by a shortening of the resilient arm 34 due to an increase inthe bend in the central portion thereof. The dimensions of the plunger40 and the spacing of the fixed contacts 22 and 24 and the free end ofresilient arm 34 are arranged so that a normally closed position ismaintained between the contacts 24 and 30 under the impetus of thespring 42 while a normally open condition is maintained between thecontacts 22 and 32.

The mounting elements 26, 28, and 35 are held in place by means ofprojecting lugs which engage opposing edges of the housing 10. Referringto FIG. 1, mounting element 26 has upper lugs 25 and 29 and the lowerlugs 31 and 33..The upper lugs 25 and 29 rest upon a thickened portionof the housing 10 and the lower lugs 31 and 33 are bent outwardly toengage the bottom of housing 10. Mounting element 35 has upper lugs 37and 39 and lower lugs 41 and 43 for engaging the housing 10 asdescribed'above. Mounting element 28 has similar lugs but they are notvisible in the drawings.

Although this invention has been described in connection with onespecific embodiment thereof, it should be understood that the inventionis not limited to the disclosed embodiment, since many modifications canbe made in the disclosed structure without departing from the basicprinciples of operation set forth in this application. For example,although a two-pole switch having two pairs of matching contacts hasbeen disclosed, it will be clear to those skilled in the art that thisinvention is also applicable to single-pole switches having only asingle pair of contacts and to multi-pole switches having three or morepairs of contacts. This and many other similar modifications of theinvention will be apparent to those skilled in the art and thisinvention includes all such modifications falling within the scope ofthe following claims.

What I claim is:

1. An electrical switch comprising a support; a first fixed electricalcontact mounted on said support; a resilient arm mounted on said supportwith one end of said arm being movable and positioned opposite saidfirst electrical contact; an inner electrical contact attached to themovable end of said resilient arm on the side facing said first fixedelectrical contact; an outer electrical contact on the other side ofsaid arm; a mounting element projecting from said support and having asecond fixed electrical contact positioned to be normally engaged bysaid outer contact of the arm, said resilient arm-having a centralportion bowed outwardly; an actuating plunger engaging the bowed por-'tionof the resilient arm and mounted for movement transverse to thedirection of extent of said resilient arm toward the support for movingsaid outer electrical contact of the arm away from saidnormally engagedsecond fixed electrical contact into engagement with the first fixedelectrical contact while flattening out the bowed portion of theresilient arm and while causing a transverse wiping movement of saidfirst electrical con tact; spring means normally urging saidactuatingplunger and said resilient arm to move in a return directionback into engagement with said second fixed electrical contact, saidspring means being positioned to act on the bowed portion of theresilient arm during such return movement to permit a shortening of theresilient arm and a wiping of said second fixed contact during suchshortening.

2. An electrical switch as claimed in claim 1 in which the actuatingplunger has an actuatable portion outwardly of the resilient arm and hasa slot through which the bowed portion of the resilient arm slideablyextends, and has an inner plunger portion inwardly of the resilient arm,the supporthaving a socket with a portion shaped to receive and guidesaid inner plunger portion, and in which said spring means is a coilspring surrounding said inner plunger portion, said socket having anenlarged portion forming a pocket for one end of said coil spring. I I

3. An electrical switch as claimed in claim 2 in which the support is inthe form of a cup-shaped casing, and in which the socket is formed inand projects outwardly from the bottom of the cup and has a firstenlarged portion forming the spring pocket and a reduced diameterportion guiding said inner plunger portion.

4. An electrical switch as claimed in claim 2 in which the inner plungerportion which is within the spring pocket is surrounded by the coilspring and of downwardly-tapered form to minimize frictional contactwith said spring.

5. An electrical switch as claimed in claim 4 in which the spring pocketportion of the socket has sides tapered in a direction to minimizerubbing contact during flexing of the coil spring.

6. An electrical switch as claimed in claim 3 in which there areelectrical terminals projecting from the bottom of the cup, one on eachside of said socket.

1. An electrical switch comprising a support; a first fixed electrical conTact mounted on said support; a resilient arm mounted on said support with one end of said arm being movable and positioned opposite said first electrical contact; an inner electrical contact attached to the movable end of said resilient arm on the side facing said first fixed electrical contact; an outer electrical contact on the other side of said arm; a mounting element projecting from said support and having a second fixed electrical contact positioned to be normally engaged by said outer contact of the arm, said resilient arm having a central portion bowed outwardly; an actuating plunger engaging the bowed portion of the resilient arm and mounted for movement transverse to the direction of extent of said resilient arm toward the support for moving said outer electrical contact of the arm away from said normally engaged second fixed electrical contact into engagement with the first fixed electrical contact while flattening out the bowed portion of the resilient arm and while causing a transverse wiping movement of said first electrical contact; spring means normally urging said actuating plunger and said resilient arm to move in a return direction back into engagement with said second fixed electrical contact, said spring means being positioned to act on the bowed portion of the resilient arm during such return movement to permit a shortening of the resilient arm and a wiping of said second fixed contact during such shortening.
 2. An electrical switch as claimed in claim 1 in which the actuating plunger has an actuatable portion outwardly of the resilient arm and has a slot through which the bowed portion of the resilient arm slideably extends, and has an inner plunger portion inwardly of the resilient arm, the support having a socket with a portion shaped to receive and guide said inner plunger portion, and in which said spring means is a coil spring surrounding said inner plunger portion, said socket having an enlarged portion forming a pocket for one end of said coil spring.
 3. An electrical switch as claimed in claim 2 in which the support is in the form of a cup-shaped casing, and in which the socket is formed in and projects outwardly from the bottom of the cup and has a first enlarged portion forming the spring pocket and a reduced diameter portion guiding said inner plunger portion.
 4. An electrical switch as claimed in claim 2 in which the inner plunger portion which is within the spring pocket is surrounded by the coil spring and of downwardly-tapered form to minimize frictional contact with said spring.
 5. An electrical switch as claimed in claim 4 in which the spring pocket portion of the socket has sides tapered in a direction to minimize rubbing contact during flexing of the coil spring.
 6. An electrical switch as claimed in claim 3 in which there are electrical terminals projecting from the bottom of the cup, one on each side of said socket. 